The invention pertains to a valve arrangement for controlling a plurality of loads all supplied by a common engine-driven constant displacement pump.
Such valve arrangements are known (DE-OS 3,443,354 or 3,512,348) and serve to simplify a hydraulic system in so far as to supply the consumers with fluid a constant displacement pump can be used via the speed of rotation of which the volumetric displacement is variable. By the pressure-regulating valve via the actuator cylinder of the speed regulator of the engine or motor driving the constant pump the speed and thus the volumetric displacement is adjusted so that the loads can be adequately supplied with fluid. If however a consumer or load is actuated which has a greater requirement of fluid the pressure-regulating valve must increase the control pressure for the actuator cylinder to increase the pump speed and thus its volumetric displacement. In known manner on deflection of the valve moveable element of the directional control valve controlling said consumer an orifice at the directional control valve is opened through which the control pressure acting on the pressure-regulating valve is decreased to the tank. As a result the pressure-regulating valve is adjusted by its regulating spring and generates the desired higher control pressure for the actuator cylinder of the speed regulator. It is further known to tap the load pressure occurring at the consumer and to conduct it to the pressure-regulating valve in the sense of increasing the control pressure.
The invention provides a simple and reliable solution to the problem of increasing engine or drive speed upon actuation of a specific consumer or consumers.